The present invention relates to an image formation apparatus, and printer, copying machine, and a facsimile device using the image formation apparatus.
A sheet feeding structure of a conventional image forming device is generally formed with a sheet separation/feeding unit that separates and feeds sheets stacked and stored in a sheet storage section one by one, a sheet conveying path that conveys the separated and fed sheet toward an image forming section, and regist rollers disposed at a position immediately before the image forming section on the sheet conveying path.
The sheet separated and fed by the sheet separation/feeding unit is conveyed along the sheet conveying path, is stopped temporarily at the position where the sheet comes into contact with the regist rollers, and fed into the image forming section at a timing at which an image is formed on an appropriate position of the sheet.
If a sheet is fed out by the regist rollers and the rear edge of this sheet and the front edge of a subsequent sheet overlap each other, these two sheets are fed into the image forming section in their overlapping state. Accordingly, one image is disadvantageously formed over the two sheets, therefore, image formation cannot be successfully performed on the sheet. Further, when the overlapping two sheets are fed into the image forming section, a sensor for detecting a sheet size detects that the sheet size is irregular, and the image forming operation is interrupted.
Therefore, when image formation is continuously performed, it has been required to widen each space between fore-and-aft sheets, and to separate and feed the sheets so that the two sheets are prevented from overlapping each other even if the subsequent sheet is fed when the preceding sheet stops at the regist rollers.
Further, in the sheet feeding structure of the conventional image forming device, a space between fore-and-aft sheets is widened by tens of millimeters and the sheets are fed when image formation is continuously performed considering that a slip may occur at the time of sheet separation and feeding by the sheet separation/feeding unit, a sheet conveying speed may be changed over time or depending on environment, or there may be variations in suspended time for registration. Therefore, it is difficult to improve productivity of image formation.
An image forming section based on an electrophotographic system cannot stop the operation because of its structure even when the sheet is not conveyed to the image forming section, and the section performs no-load operation. Therefore, a large space between continuously fed sheets makes longer the time for no-load operation, thus the life of the device is decreased so that the printing number of sheets becomes less than a possible printing number of sheets that the device originally has.
For the above-mentioned reasons, the applicants of this application have proposed an image formation apparatus with a reversing path and a sheet reversing unit provided in some midpoint of a sheet conveying path in Japanese patent application No. 11-239672 and Japanese patent application No. 2000-230153, or the like. More specifically, this image formation apparatus is capable of improving operating efficiency in image formation by narrowing a space between sheets fed into an image forming section when the image formation is continuously performed.
In accordance with the image formation apparatus provided with these reversing path and sheet reversing unit, a sheet separated and fed from a sheet storage section and conveyed along the sheet conveying path is fed into the reversing path, and the sheet is stopped temporarily on the reversing path and then switched back to be fed into the image forming section. Further, a subsequent sheet is fed into the reversing path while the sheet fed into the reversing path is switched back and is forwarded toward the image forming section. The subsequent sheet is started to be fed out from the reversing path toward the image forming section at a timing at which the preceding sheet to be forwarded to the image forming section reaches a predetermined position. Accordingly, the space between the sheets continuously fed into the image forming section can be narrowed, which makes it possible to improve the operating efficiency in image formation. Furthermore, in the image forming section, since the time for no-load operation without image formation is reduced, reduction in the life of the device due to no-load operation can be prevented.
However, according to the image formation apparatus with the reversing path and the sheet reversing unit disposed on some midpoint of the sheet conveying path, it is necessary to reliably switch a sheet conveying direction from the sheet conveying path to the reversing path, and from the reversing path to the sheet conveying path leading to the image forming section. Unsuccessful performance of this switching causes a jam to occur.
With regard to a structure of the sheet reversing unit that feeds a subsequent sheet into the reversing path while a preceding sheet is fed out from the reversing path, there have been requests for a structure that does not produce noise, a simple structure, or a structure such that sheets are fed out reliably.
When the space between fore-and-aft sheets is to be narrowed by switching back the sheet to be forwarded to the image forming section on the reversing path, it is required to set sheet conveying force by conveying rollers to be high in order not to decrease a sheet conveying speed to a value lower than a set value due to conveying load that acts on the sheet during its conveyance. However, by setting the sheet conveying force to be high, there may be such inconvenience that noise may easily be produced or power consumption may easily be increased. Further, by setting the sheet conveying force to be high, there may occur a problem that the front edge of a sheet that is rigid is forcefully pushed into a nip part of the regist rollers when they are stopped rotating and a position for image formation on the sheet is displaced.
It is an object of this invention to reliably perform switching between conveying directions of each sheet coming into or going away from a reversing path by reducing a space between sheets continuously fed into an image forming section using a reversing path and a sheet reversing unit.
Another object of this invention is to make compact a structure to switch between conveying directions of each sheet coming into or going away from the reversing path by reducing a space between conveyed sheets using the reversing path and the sheet reversing unit.
A further object of this invention is to simplify a structure to switch between conveying directions of each sheet coming into or going away from the reversing path by reducing a space between conveyed sheets using the reversing path and the sheet reversing unit.
A still further object of this invention is to reduce noise due to feeding out of a sheet from the reversing path by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to allow sheets to smoothly come into and go away from the reversing path by reducing a space between the sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to simplify a structure of the sheet reversing unit by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to reliably feed out a sheet from the reversing path by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to prevent occurrence of noise due to sheet conveyance by reducing sheet conveying force when the sheet is conveyed from the reversing path toward the image forming section.
A still further object of this invention is to reduce power consumption due to sheet conveyance by reducing sheet conveying force when the sheet is conveyed from the reversing path toward the image forming section.
A still further object of this invention is to prevent excessive sheet conveying force from acting on a sheet conveyed from the reversing path toward the image forming section.
In the image formation apparatus according to one aspect of this invention, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. A feeding unit feeds the sheet conveyed along the sheet conveying path to a reversing path, and a sheet reversing unit switches back the sheet to feed it out from the reversing path to the sheet conveying path. The sheet is then fed into an image forming section, where image formation is performed.
Feeding a subsequent sheet into the reversing path can be performed while a preceding sheet is fed out from the reversing path and forwarded to the image forming section. Therefore, feeding out the subsequent sheet from the reversing path to the image forming section can be started at the timing at which the preceding sheet is fed into a predetermined position leading to the image forming section, so that a space between the sheets continuously fed into the image forming section can be reduced, thus improving the operating efficiency in image formation.
The feeding unit feeds the sheet into the reversing path by conveying the sheet along a first guide surface of a branching claw that has been switched to a first switching position. On the other hand, the feeding unit feeds out the sheet from the reversing path by conveying the sheet along a second guide surface of the branching claw that has been switched to a second switching position. Accordingly, switching between conveying directions of each sheet coming into or going away from the reversing path can be reliably performed by using the branching claw.
Further, an inlet roller can impart conveying force to a sheet to be fed into the reversing path.
Further, the branching claw and the inlet roller are positioned close to each other. Therefore, a structure to switch between the sheet conveying directions becomes compact by using the branching claw and the inlet roller.
Further, the sheet fed out from the reversing path can be reliably prevented from entering into a nip between the outer circumferential surface of the inlet roller and the first guide surface of the branching claw, and occurrence of a jam caused by such entrance can be prevented.
Further, by pressing a sheet to be fed into the reversing path against the outer circumferential surface of the inlet roller, conveying force can be imparted to the sheet from the rotated inlet roller, thus impartation of the conveying force to the sheet can be performed with a simple structure.
Further, when a sheet is to be fed into the reversing path, the branching claw is turned from the second switching position to the first switching position by the rigidness of the sheet, and the branching claw automatically returns to the second switching position by the biasing force of the biasing unit when the feeding the sheet into the reversing path is finished. Therefore, the structure to switch the branching claw between the first switching position and the second switching position becomes so simple that only the biasing unit is provided. Furthermore, switching of the branching claw from the first switching position to the second switching position can be quickly and accurately performed in response to finishing of feeding the sheet into the reversing path.
Further, one side of a sheet to be fed into the reversing path is in contact with the outer circumferential surface of the inlet roller, and the other side of the sheet is in contact with the driven roller and the first guide surface of the branching claw. Through this contact of the sheet with the driven roller, the conveying force to be imparted to the sheet can be more increased as compared to the case where the other side of the sheet contacts only the first guide surface of the branching claw, thus smoothly feeding the sheet into the reversing path.
Further, a part of the driven roller projecting from the second guide surface of the branching claw rotates in a sheet forwarding direction that feeds out a sheet along the second guide surface from the reversing path. Therefore, feeding out the sheet from the reversing path can be promoted when the projecting part of the driven roller contacts the surface of the sheet fed out of the reversing path.
The projecting dimension of the driven roller from the second guide surface of the branching claw that is located at the second switching position is a radius or less of the driven roller. Therefore, even when the front edge of the sheet fed out of the reversing path comes into contact with the outer circumferential surface of the driven roller, the front edge of the sheet can be prevented from entering into a nip between the outer circumferential surface of the driven roller and the second guide surface of the branching claw.
Further, the need for a dedicated shaft to support the driven roller is eliminated, thus obtaining a compact structure.
In the image formation apparatus according to another aspect of this invention, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. The sheet conveyed along the sheet conveying path is fed into a reversing path, and a sheet reversing unit switches back the sheet to feed it out from the reversing path to the sheet conveying path. The sheet is then fed into an image forming section, where image formation is performed.
Feeding a subsequent sheet into the reversing path can be performed while a preceding sheet is fed out from the reversing path and forwarded to the image forming section. Therefore, feeding out the subsequent sheet from the reversing path toward the image forming section can be started at the timing at which the preceding sheet is fed into a predetermined position leading to the image forming section, so that a space between the sheets continuously fed into the image forming section can be reduced, thus improving the operating efficiency in image formation.
The driven roller coming into contact with the outer circumferential surface of the inlet roller is rotated with rotation of the inlet roller, and the sheet is nipped with the driven roller and the inlet roller to be fed into the reversing path. This driven roller rotates in a direction that forwards the sheet fed out from the reversing path toward the image forming section positioned on the downstream side of the sheet conveying path. Therefore, even when the sheet fed out of the reversing path touches the driven roller, the sheet can be smoothly fed out from the reversing path. Accordingly, switching between the conveying directions of each sheet coming into or going away from the reversing path can be reliably performed with a simple structure having the inlet roller and the driven roller that comes into contact with the outer circumferential surface of the inlet roller and rotates together with the inlet roller.
Further, even when the front edge of the sheet fed out of the reversing path touches the outer circumferential surface of the driven roller, the sheet proceeds along the outer circumferential surface of the driven roller in the direction that forwards the sheet toward the image forming section positioned on the downstream side of the sheet conveying path. Thus, the sheet can be prevented from entering into a nip between the outer circumferential surface of the driven roller and the outer circumferential surface of the inlet roller.
Further, even when the front edge of the sheet touches any part, that is close to the inlet roller, on the outer circumferential surface of the driven roller caused by a curl or a folded part of the front edge of the sheet fed out of the reversing path, the sheet front edge is caught by a sheet front edge catching part formed on the outer circumferential surface of the driven roller. Therefore, the sheet front edge is conveyed to a position, with the rotation of the driven roller, where the sheet is forwarded toward the image forming section positioned on the downstream side of the sheet conveying path, thus smoothly forwarding the sheet fed out of the reversing path.
In the image formation apparatus according to still another aspect of this invention, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. The sheet conveyed along the sheet conveying path is fed into a reversing path, and a sheet reversing unit switches back the sheet to feed it out from the reversing path to the sheet conveying path. The sheet is then fed into an image forming section, where image formation is performed.
Feeding a subsequent sheet into the reversing path can be performed while a preceding sheet is fed out from the reversing path and forwarded to the image forming section. Therefore, feeding out the subsequent sheet from the reversing path to the image forming section can be started at the timing at which the preceding sheet is fed into a predetermined position leading to the image forming section, so that a space between the sheets continuously fed into the image forming section can be reduced, thus improving the operating efficiency in image formation.
The sheet is fed into the reversing path in a state where the sheet is nipped with the inlet roller and a belt. Therefore, a nip width of the sheet nipped with the inlet roller and the belt can be widened, thus smoothly feeding even a rigid sheet into the reversing path.
Further, the sheet fed out of the reversing path can be prevented from entering into the nip between the outer circumferential surface of the inlet roller and the belt, thus smoothly forwarding the sheet fed out from the reversing path.
Further, a larger conveying force can be imparted to the sheet through rotation of the belt, thus more smoothly feeding the sheet into the reversing path.
In the image formation apparatus according to still another aspect of this invention, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. The sheet conveyed along the sheet conveying path is fed into a reversing path, and a sheet reversing unit switches back the sheet to feed it out from the reversing path to the sheet conveying path. The sheet is then fed into an image forming section, where image formation is performed.
Feeding a subsequent sheet into the reversing path can be performed while a preceding sheet is fed out from the reversing path and forwarded to the image forming section. Therefore, feeding out the subsequent sheet from the reversing path toward the image forming section can be started at the timing at which the preceding sheet is fed into a predetermined position leading to the image forming section, so that a space between the sheets continuously fed into the image forming section can be reduced, thus improving the operating efficiency in image formation.
The sheet enters, by the rigidness of its own, into the nip between the outer circumferential surface of the inlet roller and a blade, and is imparted with the conveying force from the inlet roller to be fed into the reversing path. Furthermore, the sheet is fed out of the reversing path so that the sheet proceeds along the rear side of the blade whose the other side is in contact with the inlet roller. Therefore, switching between the conveying directions of each sheet coming into or going away from the reversing path can be reliably performed with a simple structure having the inlet roller and the blade that is pressed against the outer circumferential surface of the inlet roller.
Further, there is no need to additionally provide a unit for pressing the blade against the outer circumferential surface of the inlet roller, thus obtaining a simpler structure.
Further, the blade can be made of a high slip material, thus smoothly feeding the sheet into the reversing path by passing the sheet through between the inlet roller and the blade.
Further, the blade is in close contact with the outer circumferential surface of the inlet roller, and the sheet fed out of the reversing path can be prevented from being caught on the blade, thus smoothly switching between the sheet conveying directions.
Further, the sheet fed out of the reversing path can be more reliably prevented from being caught on the blade, thus more smoothly switching between the sheet conveying directions.
Further, a subsequent sheet can be in a standby state where the sheet is ready to be fed out of the reversing path during feeding out of a preceding sheet from the reversing path. Therefore, when the subsequent sheet is switched back to be fed out of the reversing path, the required smallest possible space with the preceding sheet can be surely maintained, thus making sufficiently smaller the space between the sheets continuously fed into the image forming section.
Further, in accordance with the image formation apparatus, the reversing path is formed in a direction substantially perpendicular to the sheet conveying path formed in a vertical direction between the sheet storage section and the image forming section. Therefore, this reversing path can be formed so as to be positioned within a projection plane of the image forming section. Accordingly, the lateral dimension of the image formation apparatus is not increased despite formation of such a reversing path, thus achieving minimization of the image formation apparatus in lateral dimension.
Further, the image formation apparatus provided with the image forming section based on an electrophotographic system obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
Further, the image formation apparatus provided with the image forming section based on a digital electrophotographic system with a digital writing unit obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
The copying machine according to still another aspect of this invention also obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
In the image formation apparatus according to still another aspect of this invention, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. The sheet conveyed along the sheet conveying path is fed into a reversing path, and a sheet reversing unit switches back the sheet to feed it out from the reversing path to the sheet conveying path. The sheet is then fed into an image forming section, where image formation is performed.
Feeding a subsequent sheet into the reversing path can be performed during feeding out of a preceding sheet from the reversing path. Therefore, feeding out the subsequent sheet from the reversing path toward the image forming section can be started at the timing at which the preceding sheet is fed into a predetermined position leading to the image forming section, so that a space between the sheets continuously fed into the image forming section can be reduced, thus improving the operating efficiency in image formation.
The sheet is fed out of the reversing path by nipping the sheet with a part except a low friction part of a reverse roller and a driven roller and rotating the reverse roller. Therefore, the sheet can be smoothly fed out by imparting the sufficient conveying force to the sheet. Furthermore, at the time of feeding out the sheet from the reversing path, only the reverse roller is rotated. Therefore, occurrence of noise due to a collision between the reverse roller and the driven roller can be prevented.
When no more conveying force needs to be imparted to the sheet from the reverse roller because the sheet has been forwarded to a predetermined position, the reverse roller is stopped to be rotated at a position where the low friction part of the reverse roller faces the driven roller. Frictional resistance with respect to the sheet passing through between these low friction part of the reverse roller and driven roller is low. Therefore, even when the rear side of the sheet fed out of the conveying path in the forwarding direction is nipped with the low friction part and the driven roller, the sheet smoothly proceeds. Furthermore, the subsequent sheet can be smoothly fed into the nip between the low friction part of the reverse roller and the driven roller.
Further, a subsequent sheet can be in a standby state where the sheet is ready to be fed out of the reversing path during feeding out of a preceding sheet from the reversing path. Therefore, when the subsequent sheet is switched back to be fed out of the reversing path, the required smallest possible space with the preceding sheet can be surely maintained, thus making sufficiently smaller the space between the sheets continuously fed into the image forming section.
Further, by facing a flat part toward the driven roller, a space between the reverse roller and the driven roller is produced. Therefore, even when the rear side of the sheet fed out of the reversing path in the forwarding direction is left between the reverse roller and the driven roller, the frictional resistance is not imparted to the sheet, thus smoothly feeding out the sheet. Furthermore, a subsequent sheet is allowed to enter into the space between the flat part and the driven roller and is capable of being fed into the reversing path during feeding out of the preceding sheet from the conveying path.
Further, a driving section can rotate the reverse roller, and a rotational position detecting unit can detect a rotational position of the reverse roller. Therefore, rotation and stop of the reverse roller can be controlled with high precision.
Further, a rotation stop position of the reverse roller can be more precisely controlled, which makes it possible to surely stop the reverse roller at a position where the flat part faces the driven roller.
Further, when the sheet is fed out of the reversing path, uniform force can be applied to the sheet in its lateral direction, thus preventing a skew of the sheet to be fed out.
Further, one wide roller part is provided to make simpler the structure of the reverse roller.
Further, it is possible to prevent occurrence of a slip at the time of feeding out the sheet from the reversing path, thus precisely feeding out the sheet from the reversing path.
Further, a holding structure of the reverse roller and the driven roller becomes simple.
Further, even if sheets have different thickness, the sheet can securely be nipped with the reverse roller and the driven roller, so that feeding out of the sheet can be surely performed. Furthermore, the driving unit is not coupled to the driven roller. Therefore, even when the driven roller is held movably in directions that contacts and moves away from the reverse roller, the holding structure becomes simple.
Further, the sheet fed out of the reversing path can be securely nipped with the reverse roller and the driven roller. Furthermore, it is possible to prevent occurrence of a skew caused by heavy rubbing of the sheet fed out from the conveying path with the sheet guide surface.
Further, the detection result of a detection sensor can be used as a trigger, thus precisely controlling the timing of reversing the reverse roller.
Further, a detection sensor is positioned at a place close to the reversing path. Therefore, it is possible to precisely control the timing of reversing the reverse roller by using the result of detection from this detection sensor as a trigger for a driving unit.
Further, the time since the detection sensor detects the sheet until the reverse roller is reversed can be reduced. Therefore, it is possible to more precisely control the timing of driving the reverse roller by using the result of detection from this detection sensor as a trigger for the driving unit.
Further, the image formation apparatus having the image forming section based on the electrophotographic system obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
Further, the image formation apparatus having the image forming section based on the digital electrophotographic system with the digital writing unit obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
Further, the image formation apparatus having an image forming section based on a non-electrophotographic system obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
Further, the image formation apparatus, that performs image formation on a card, obtains the same advantageous effect as that of any of the above-mentioned aspects of this invention.
The printer according to still another aspect of this invention can also obtain the same advantageous effect as that of any of the above-mentioned aspects of this invention.
The copying machine according to still another aspect of this invention can also obtain the same advantageous effect as that of any of the above-mentioned aspects of this invention.
The facsimile device according to still another aspect of this invention can also obtain the same advantageous effect as that of any of the above-mentioned aspects of this invention.
Further, in the image formation apparatus, a sheet separation/feeding unit separates and feeds sheets stacked and stored in a sheet storage section one by one, and the sheet is conveyed along a sheet conveying path. The sheet conveyed along the sheet conveying path is fed into a reversing path, where the sheet is temporarily stopped, and a sheet reversing unit then switches back the sheet to feed it out from the reversing path to an image forming section. Image formation is perform on the sheet fed into the image forming section.
Feeding a subsequent sheet into the reversing path is performed during feeding out of a preceding sheet from the reversing path when the sheet reversing unit is brought to an open state. Therefore, when the subsequent sheet is fed out of the reversing path, a space between the two sheets successively fed into the image forming section can be reduced with stability by controlling a sheet forwarding timing and a sheet forwarding speed, thus improving the operating efficiency in image formation.
The sheet fed out of the reversing path is captured by intermediate conveying rollers immediately before the sheet reversing unit is brought to the open state. These intermediate conveying rollers convey the sheet, whose rear side in its conveying direction is released, toward the image forming section.
The intermediate conveying rollers nip and convey the sheet whose rear side in the conveying direction is released, so that conveying load is not acted on the sheet during this conveyance. Therefore, even if the sheet conveying force of the intermediate conveying rollers is reduced, sheet conveyance can be smoothly performed. Furthermore, by reducing the sheet conveying force, occurrence of noise due to the sheet conveyance can be prevented, and power consumption required for the sheet conveyance can be reduced.
Further, the sheet reversing unit consisting of the reverse roller and the driven roller is brought to a sheet forwarding state when the driven roller is brought into contact with the outer circumferential surface of the reverse roller and is rotated together with the reverse roller, and is brought to an open state when the flat part of the reverse roller faces the driven roller to produce a space between the flat part and the outer circumferential surface of the driven roller.
Further, the sheet reversing unit is brought to a sheet forwarding state when a beat roller pair is moved to a position where the outer circumferential surfaces of the beat roller pair come into contact with the sheet to nip the sheet, and is brought to an open state when the roller pair is moved to a position where it is separated away from the sheet.
Further, when the intermediate conveying rollers enter into a state where an excessive sheet conveying force is acted on the rollers, no-load operation occurs in a toque limiter. Therefore, an excessive sheet conveying force is prevented from acting on the sheet conveyed from the reversing path toward the image forming section.
Further, after the front edge of the sheet conveyed by the intermediate conveying rollers comes into contact with regist rollers disposed at a position immediately before the image forming section, the intermediate conveying rollers become slippery with respect to the sheet. Thus, the sheet front edge can be prevented from being pushed into the nip part between the regist rollers or from being folded due to impartation of the excessive sheet conveying force from the intermediate conveying rollers to the sheet.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.